1. Field of the Invention
This invention relates to the detection of leaks from buried pipes.
2. Introduction to the Invention
It is well known that there is a need to prevent leaks from buried pipes, to detect such leaks if they occur, and, if possible, to contain such leaks when the fluid is harmful to the environment, e.g. is a hydrocarbon. A very common way of preventing corrosion of metal pipes is by means of cathodic protection systems, and these require that when the soil is wet, there is a continuous electrical path from the cathode to the pipe. Many systems have been proposed for detecting leaks, including those disclosed in U.S. Pat. Nos. 4,843,327 (Koppitsch et al.), 4,862,146 (McCoy et al.), 4,922,183 (Kamas), 4,926,129 (Wasley et al.), 4,926,165 (Lahlouh et al.), 4,931,741 (Koppitsch et al.), 5,015,958 (Masia et al.), 5,101,657 (Lahlouh et al.), 5,191,292 (Klotz et al.), 5,235,286 (Masia et al.), and 5,382,909 (Masia et al.), the disclosures of which are incorporated herein by reference for all purposes. However, when such leak detectors are placed adjacent to a directly buried pipe, absorption of the leaking fluid by the soil can render the system ineffective. In order to ensure that a sufficient amount of the leaking fluid contacts the leak detector to activate the system (and in order to contain the leaking fluid), double containment systems have been used. However, double containment systems are slow and expensive to install, and interfere with cathodic protection systems.